so we did some parts testing tonight on a buddies 07 balt. we put my 2.7 on his car and left the stock injectors in to see what would happen. his baseline (mustang dyno) was 215whp injector duty cycle was roughly 30%
we put on the 2.7 and he made 235whp on the stockers. the injector duty cycle was 70% all the way to 7K and air fuel ratio was 11.8-12.2 all the way to redline. all the tests we did where on a mustang dyno. his mods are 3 inch catback with a magnaflow race muffler and a XTC intake my ported blower and the 2.7, the car was making 17.4 PSI we did multiple passes to make sure it wasnt a fluke. needless to say i lost the bet i thought it was gonna see over 100% duty cycle. but i also thought the car was going to make 260whp. im in no way saying this will work on everyones car, but on his its working like a charm, i wouldnt believe it if i wasnt there for 6 1/2 hours working on the car and doing dyno runs!
the dyno pulls where done at backwoods racing in midland michigan, if you have doubts ill give you the number to the dyno oporator, he is a buddy of mine and he will vouch for it.

 

Umm... What. How is this possible? Less timing?

 

Depending on area and weather, I can see as to how that is possible. I wouldn't go that small of a pulley, even with a tune. One surprise cold snap and BANG!!

 

What elevation are you at with those idc's on t he dyno?

 

sea level, we are in michigan.

 

Michigan is at sea level..?? wtf....its like 580ft

sorry, the lake doesn't count.

 

LOL @ Doc

 

my bad, google says the mean elevation is 900 feet above sea level.

 

Hey donny that pretty impressive So what mitch think about it

 

we where expecting bigger numbers, and the seat of the pants dyno says its not as fast on his car as it was on mine.

 

I am trying to get me a nates 2.9 pulley and then go get dynoed and tuned there

 

You throw some 60's in there, then you will be able to throw some more timing in as well which may help that issue. My car likes to post low numbers on the dyno as well, but she is a whole nother beast on the street. I think she likes to play mind games like that. lol

 

One of our problems is pump gas is only 91 octane here and it was pulling alot of timing and using the low octane map/file or whatever its called in hptuners. It was pulling like 8-10 degrees through the whole pull. My dyno guy said with our 2.85 pulley and at sea level we need 60 lb'ers and better gas our afm was also around 14.65 at 3500 and went flat the rest of the way at 12.80 from 4200-6400 or so. Our IDC's, hit 92% at 5600, 95% at 6000 and 117% at 6300 rpms with 42 lb injectors. Defiantly needs some work.

 

interesting, i still think alot of peoples worries about the 42lb injectors are just innacuracies with hptuners.

 

this must only be to 6,500rpm. i cant see this happening at 7k

i experiebced 0 problems with my 2.9 on the stock injectors (it actually felt faster than after the 42s)

 

I've been seeing 70% IDC with 60's and a 2.7

 

Yes and I've talked to hptuners about this and they say no to that comment. Our problems are crap octane of only 91 if that in this area. Throw some 95 octane in it and its night and day difference.

 

well i have 93 octane here. BUt to me it just seems retarded that GM would put out an upgrade kit with the injectors at like 85% IDC. Just seems like GM would be smart enough to realise this, and also realise people are going to want to upgrade to a smaller pulley and if they do they run a huge risk of blowing their engine. Then hopefully they would also realise they warrantied the upgrade and would have to be doing alot of warranty work.

Also has anyone blown up their engine with 42lb injectors and GM stage 2 tune yet? Or even with 42lb injectors?

 

Interesting. I wouldn't goto a 2.7" but a 3" may be something to try. Hmmmm

 

Gm knew 42 lb injectors work just fine with their stage 2 pulley thats why the warranty was still good withthe upgrade. They gave themselves plenty of room also, so even going with a 2.9 pulley would work just fine also.

 

the pulls where on 93 octane, and the revs where to 7K

 

your injector tables are wrong.

 

the only thing that was throwing me off was the injector pulse width i guess never went dangerous, and the A/F ratio never got dangerous, hell the car is actualy rich right now!

 

something is not right. the car has to be bleeding off the boost or something.

 

give it time. the injectors are weak. soon the a/s will go nuts and start spiking at 6k rpms. the duty cycle, or the milliseconds will not show this, but the a/f will. soon after this. if it is not helped in some way. the motor will go south.

the reason i say this, is he fact that mine started like this. i didn't catch it on the data logger, but the lm1 showed it plain as day.